/**
 * Bounded LRU of `WebGLTexture` keyed by tile cache key (see
 * `tile-loader.tileKey`). Evicts least-recently-touched entries on
 * insert past `capacity`, deleting their GPU textures.
 *
 * Default capacity of 256 is enough to cover a full screen worth of
 * tiles at zoom-1 jumps either side of the current viewport plus the
 * parent fallbacks — at 256×256 RGBA that's ~64 MB of texture memory,
 * which sits comfortably under the 256 MB headroom most browsers
 * grant to a tab.
 */
export declare class TileCache {
    private _entries;
    private readonly _capacity;
    constructor(capacity?: number);
    /**
     * Fetch a texture by key. Touching an existing entry moves it to
     * the LRU tail so it survives the next eviction sweep.
     */
    get(key: string): WebGLTexture | undefined;
    /**
     * Insert a texture under `key`. If the cache is at capacity, evict
     * the oldest entry first (calling `gl.deleteTexture` on its GPU
     * resource).
     */
    set(gl: WebGL2RenderingContext | WebGLRenderingContext, key: string, texture: WebGLTexture): void;
    /**
     * Whether a key is resident. Used to gate the "kick off a fetch"
     * branch in the layer's render loop.
     */
    has(key: string): boolean;
    /**
     * Release every texture. Called on chart destroy. Safe to call
     * with a stale `gl` reference (no-op if `deleteTexture` rejects),
     * but in practice the caller passes the still-live worker context.
     */
    dispose(gl: WebGL2RenderingContext | WebGLRenderingContext): void;
}